Pneumonia

Pneumonia

Pneumonia is an inflammatory illness of the lung.[1] Frequently, it is described as lung parenchyma/alveolar inflammation and abnormal alveolar filling with fluid (consolidation and exudation).[2]

The alveoli are microscopic air-filled sacs in the lungs responsible for absorbing oxygen. Pneumonia can result from a variety of causes, including infection with bacteria, viruses, fungi, or parasites, and chemical or physical injury to the lungs. Its cause may also be officially described as idiopathic—that is, unknown—when infectious causes have been excluded.

Typical symptoms associated with pneumonia include cough, chest pain, fever, and difficulty in breathing. Diagnostic tools include x-rays and examination of the sputum. Pneumonia Treatment depends on the cause of pneumonia; bacterial pneumonia is treated with antibiotics.

Pneumonia is a common illness which occurs in all age groups, and is a leading cause of death among the elderly and people who are chronically and terminally ill. Additionally, it is the leading cause of death in children under five years old worldwide.[3] Vaccines to prevent certain types of pneumonia are available. The prognosis depends on the type of pneumonia, the appropriate treatment, any complications, and the person's underlying health.

Other types of pneumonia

Severe acute respiratory syndrome (SARS): SARS is a highly contagious and deadly type of pneumonia which first occurred in 2002 after initial outbreaks in China. SARS is caused by the SARS coronavirus, a previously unknown pathogen.
Bronchiolitis obliterans organizing pneumonia (BOOP): BOOP is caused by inflammation of the small airways of the lungs. It is also known as cryptogenic organizing pneumonitis (COP).
Eosinophilic pneumonia: Eosinophilic pneumonia is invasion of the lung by eosinophils, a particular kind of white blood cell. Eosinophilic pneumonia often occurs in response to infection with a parasite or after exposure to certain types of environmental factors.
Chemical pneumonia: Chemical pneumonia (usually called chemical pneumonitis) is caused by chemical toxicants such as pesticides, which may enter the body by inhalation or by skin contact. When the toxic substance is an oil, the pneumonia may be called lipoid pneumonia.
Aspiration pneumonia: Aspiration pneumonia (or aspiration pneumonitis) is caused by aspirating foreign objects which are usually oral or gastric contents, either while eating, or after reflux or vomiting which results in bronchopneumonia. The resulting lung inflammation is not an infection but can contribute to one, since the material aspirated may contain anaerobic bacteria or other unusual causes of pneumonia. Aspiration is a leading cause of death among hospital and nursing home patients, since they often cannot adequately protect their airways and may have otherwise impaired defenses.
Dust pneumonia: Dust pneumonia describes disorders caused by excessive exposure to dust storms, particularly during the Dust Bowl in the United States. With dust pneumonia, dust settles all the way into the alveoli of the lungs, stopping the cilia from moving and preventing the lungs from ever clearing themselves.
Necrotizing pneumonia, although overlapping with many other classifications, includes pneumonias that cause substantial necrosis of lung cells, and sometimes even lung abscess. Implicated bacteria are extremely commonly anaerobic bacteria, with or without additional facultatively anaerobic ones like Staphylococcus aureus, Klebsiella pneumoniae and Streptococcus pyogenes.[5] Type 3 pneumococcus is uncommonly implicated.[5]
Opportunistic pneumonia includes those that frequently strike immunocompromised victims. Main pathogens are cytomegalovirus, Pneumocystis jiroveci, Mycobacterium avium-intracellulare, invasive aspergillosis, invasive candidiasis, as well as the "usual bacteria" that strike immunocompetent people as well.[5]

Pneumonia Signs and symptoms

People with infectious pneumonia often have a cough producing greenish or yellow sputum, or phlegm and a high fever that may be accompanied by shaking chills. Shortness of breath is also common, as is pleuritic chest pain, a sharp or stabbing pain, either experienced during deep breaths or coughs or worsened by them. People with pneumonia may cough up blood, experience headaches, or develop sweaty and clammy skin. Other possible symptoms are loss of appetite, fatigue, blueness of the skin, nausea, vomiting, mood swings, and joint pains or muscle aches. Less common forms of pneumonia can cause other symptoms; for instance, pneumonia caused by Legionella may cause abdominal pain and diarrhea, while pneumonia caused by tuberculosis or Pneumocystis may cause only weight loss and night sweats. In elderly people manifestations of pneumonia may not be typical. They may develop a new or worsening confusion or may experience unsteadiness, leading to falls. Infants with pneumonia may have many of the symptoms above, but in many cases they are simply sleepy or have a decreased appetite.[8]

Symptoms of pneumonia need immediate medical evaluation. Physical examination by a health care provider may reveal fever or sometimes low body temperature, an increased respiratory rate, low blood pressure, a high heart rate, or a low oxygen saturation, which is the amount of oxygen in the blood as indicated by either pulse oximetry or blood gas analysis. People who are struggling to breathe, who are confused, or who have cyanosis (blue-tinged skin) require immediate attention.

Physical examination of the lungs may be normal, but often shows decreased expansion of the chest on the affected side, bronchial breathing on auscultation with a stethoscope (harsher sounds from the larger airways transmitted through the inflamed and consolidated lung), and rales (or crackles) heard over the affected area during inspiration. Percussion may be dulled over the affected lung, but increased rather than decreased vocal resonance (which distinguishes it from a pleural effusion).[8] While these signs are relevant, they are insufficient to diagnose or rule out a pneumonia; moreover, in studies it has been shown that two doctors can arrive at different findings on the same patient.[9][10]

Cause

Pneumonia can be caused by microorganisms, irritants and unknown causes. When pneumonias are grouped this way, infectious causes are the most common type.

The symptoms of infectious pneumonia are caused by the invasion of the lungs by microorganisms and by the immune system's response to the infection. Although more than one hundred strains of microorganism can cause pneumonia, only a few are responsible for most cases. The most common causes of pneumonia are viruses and bacteria. Less common causes of infectious pneumonia are fungi and parasites.

Viruses

Viruses invade cells in order to reproduce. Typically, a virus reaches the lungs when airborne droplets are inhaled through the mouth and nose. Once in the lungs, the virus invades the cells lining the airways and alveoli. This invasion often leads to cell death, either when the virus directly kills the cells, or through a type of cell controlled self-destruction called apoptosis. When the immune system responds to the viral infection, even more lung damage occurs. White blood cells, mainly lymphocytes, activate certain chemical cytokines which allow fluid to leak into the alveoli. This combination of cell destruction and fluid-filled alveoli interrupts the normal transportation of oxygen into the bloodstream.

As well as damaging the lungs, many viruses affect other organs and thus disrupt many body functions. Viruses can also make the body more susceptible to bacterial infections; for which reason bacterial pneumonia often complicates viral pneumonia.

Viral pneumonia is commonly caused by viruses such as influenza virus, respiratory syncytial virus (RSV), adenovirus, and metapneumovirus. Herpes simplex virus is a rare cause of pneumonia except in newborns. People with weakened immune systems are also at risk of pneumonia caused by cytomegalovirus (CMV).

Bacteria

Bacteria typically enter the lung when airborne droplets are inhaled, but can also reach the lung through the bloodstream when there is an infection in another part of the body. Many bacteria live in parts of the upper respiratory tract, such as the nose, mouth and sinuses, and can easily be inhaled into the alveoli. Once inside, bacteria may invade the spaces between cells and between alveoli through connecting pores. This invasion triggers the immune system to send neutrophils, a type of defensive white blood cell, to the lungs. The neutrophils engulf and kill the offending organisms, and also release cytokines, causing a general activation of the immune system. This leads to the fever, chills, and fatigue common in bacterial and fungal pneumonia. The neutrophils, bacteria, and fluid from surrounding blood vessels fill the alveoli and interrupt normal oxygen transportation.

Bacteria often travel from an infected lung into the bloodstream, causing serious or even fatal illness such as septic shock, with low blood pressure and damage to multiple parts of the body including the brain, kidneys, and heart. Bacteria can also travel to the area between the lungs and the chest wall (the pleural cavity) causing a complication called an empyema.

The most common causes of bacterial pneumonia are Streptococcus pneumoniae and "atypical" bacteria. Atypical bacteria are parasitic bacteria that live intracellular or do not have a cell wall. Moreover they cause generally less severe pneumonia, thus atypical symptoms, and respond to different antibiotics than other bacteria.

The types of Gram-positive bacteria that cause pneumonia can be found in the nose or mouth of many healthy people. Streptococcus pneumoniae, often called "pneumococcus", is the most common bacterial cause of pneumonia in all age groups except newborn infants. Pneumococcus kills approximately one million children annually, mostly in developing countries.[11] Another important Gram-positive cause of pneumonia is Staphylococcus aureus, with Streptococcus agalactiae being an important cause of pneumonia in newborn babies. Gram-negative bacteria cause pneumonia less frequently than gram-positive bacteria. Some of the gram-negative bacteria that cause pneumonia include Haemophilus influenzae, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa and Moraxella catarrhalis. These bacteria often live in the stomach or intestines and may enter the lungs if vomit is inhaled. "Atypical" bacteria which cause pneumonia include Chlamydophila pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila.

Fungi

Fungal pneumonia is uncommon, but it may occur in individuals with immune system problems due to AIDS, immunosuppresive drugs, or other medical problems. The pathophysiology of pneumonia caused by fungi is similar to that of bacterial pneumonia. Fungal pneumonia is most often caused by Histoplasma capsulatum, blastomyces, Cryptococcus neoformans, Pneumocystis jiroveci, and Coccidioides immitis. Histoplasmosis is most common in the Mississippi River basin, and coccidioidomycosis in the southwestern United States.

Parasites

A variety of parasites can affect the lungs. These parasites typically enter the body through the skin or by being swallowed. Once inside, they travel to the lungs, usually through the blood. There, as in other cases of pneumonia, a combination of cellular destruction and immune response causes disruption of oxygen transportation. One type of white blood cell, the eosinophil, responds vigorously to parasite infection. Eosinophils in the lungs can lead to eosinophilic pneumonia, thus complicating the underlying parasitic pneumonia. The most common parasites causing pneumonia are Toxoplasma gondii, Strongyloides stercoralis, and Ascariasis.

Idiopathic

Idiopathic interstitial pneumonias (IIP) are a class of diffuse lung diseases. In some types of IIP, e.g. some types of usual interstitial pneumonia, the cause, indeed, is unknown or idiopathic. In some types of IIP the cause of the pneumonia is known, e.g. desquamative interstitial pneumonia is caused by smoking, and the name is a misnomer.

Pneumonia Diagnosis

If pneumonia is suspected on the basis of a patient's symptoms and findings from physical examination, further investigations are needed to confirm the diagnosis. Information from a chest X-ray and blood tests are helpful, and sputum cultures in some cases. The chest X-ray is typically used for diagnosis in hospitals and some clinics with X-ray facilities. However, in a community setting (general practice), pneumonia is usually diagnosed based on symptoms and physical examination alone.[citation needed] Diagnosing pneumonia can be difficult in some people, especially those who have other illnesses. Occasionally a chest CT scan or other tests may be needed to distinguish pneumonia from other illnesses.

Differential diagnosis

Several diseases and/or conditions can present with similar clinical features to pneumonia and as such care must be taken in the proper diagnosis of the disease. Chronic obstructive pulmonary disease (COPD) or asthma can present with a polyphonic wheeze, similar to that of pneumonia. Pulmonary edema can be mistaken for pneumonia due to its ability to show a third heart sound and present with an abnormal ECG. Other diseases to be taken into consideration include bronchiectasis, lung cancer and pulmonary emboli.[8]

Pneumonia Prevention

There are several ways to prevent infectious pneumonia. Appropriately treating underlying illnesses (such as AIDS) can decrease a person's risk of pneumonia. Smoking cessation is important not only because it helps to limit lung damage, but also because cigarette smoke interferes with many of the body's natural defenses against pneumonia.

Research shows that there are several ways to prevent pneumonia in newborn infants. Testing pregnant women for Group B Streptococcus and Chlamydia trachomatis, and then giving antibiotic treatment if needed, reduces pneumonia in infants. Suctioning the mouth and throat of infants with meconium-stained amniotic fluid decreases the rate of aspiration pneumonia.

Vaccination is important for preventing pneumonia in both children and adults. Vaccinations against Haemophilus influenzae and Streptococcus pneumoniae in the first year of life have greatly reduced the role these bacteria play in causing pneumonia in children. Vaccinating children against Streptococcus pneumoniae has also led to a decreased incidence of these infections in adults because many adults acquire infections from children. Hib vaccine is now widely used around the globe. The childhood pneumococcal vaccine is still as of 2009 predominantly used in high-income countries, though this is changing. In 2009, Rwanda became the first low-income country to introduce pneumococcal conjugate vaccine into their national immunization program.[16]

A vaccine against Streptococcus pneumoniae is also available for adults. In the U.S., it is currently recommended for all healthy individuals older than 65 and any adults with emphysema, congestive heart failure, diabetes mellitus, cirrhosis of the liver, alcoholism, cerebrospinal fluid leaks, or those who do not have a spleen. A repeat vaccination may also be required after five or ten years.[17]

Influenza vaccines should be given yearly to the same individuals who receive vaccination against Streptococcus pneumoniae. In addition, health care workers, nursing home residents, and pregnant women should receive the vaccine.[18] When an influenza outbreak is occurring, medications such as amantadine, rimantadine, zanamivir, and oseltamivir can help prevent influenza.[19][20]

Treatment

Most cases of pneumonia can be treated without hospitalization. Typically, oral antibiotics, rest, fluids, and home care are sufficient for complete resolution. However, people with pneumonia who are having trouble breathing, people with other medical problems, and the elderly may need more advanced treatment. If the symptoms get worse, the pneumonia does not improve with home treatment, or complications occur, the person will often have to be hospitalized

Bacterial pneumonia: Antibiotics are used to treat bacterial pneumonia. In contrast, antibiotics are not useful for viral pneumonia, although they sometimes are used to treat or prevent bacterial infections that can occur in lungs damaged by a viral pneumonia.[citation needed] The antibiotic choice depends on the nature of the pneumonia, the most common microorganisms causing pneumonia in the local geographic area, and the immune status and underlying health of the individual. Treatment for pneumonia should ideally be based on the causative microorganism and its known antibiotic sensitivity. However, a specific cause for pneumonia is identified in only 50% of people, even after extensive evaluation.[citation needed] Because treatment should generally not be delayed in any person with a serious pneumonia, empiric treatment is usually started well before laboratory reports are available. In the United Kingdom, amoxicillin and clarithromycin or erythromycin are the antibiotics selected for most patients with community-acquired pneumonia; patients allergic to penicillins are given erythromycin instead of amoxicillin.[21] In North America, where the "atypical" forms of community-acquired pneumonia are becoming more common, macrolides (such as azithromycin and clarithromycin), the fluoroquinolones, and doxycycline have displaced amoxicillin as first-line outpatient treatment for community-acquired pneumonia.[22] The duration of treatment has traditionally been seven to ten days, but there is increasing evidence that shorter courses (as short as three days) are sufficient.[23][24][25]

Antibiotics for hospital-acquired pneumonia include third- and fourth-generation cephalosporins, carbapenems, fluoroquinolones, aminoglycosides, and vancomycin.[26] These antibiotics are usually given intravenously. Multiple antibiotics may be administered in combination in an attempt to treat all of the possible causative microorganisms. Antibiotic choices vary from hospital to hospital because of regional differences in the most likely microorganisms, and because of differences in the microorganisms' abilities to resist various antibiotic treatments.

People who have difficulty breathing due to pneumonia may require extra oxygen. Extremely sick individuals may require intensive care, often including endotracheal intubation and artificial ventilation.

Viral pneumonia: Viral pneumonia caused by influenza A may be treated with rimantadine or amantadine, while viral pneumonia caused by influenza A or B may be treated with oseltamivir or zanamivir. These treatments are beneficial only if they are started within 48 hours of the onset of symptoms. Many strains of H5N1 influenza A, also known as avian influenza or "bird flu," have shown resistance to rimantadine and amantadine. There are no known effective treatments for viral pneumonias caused by the SARS coronavirus, adenovirus, hantavirus, or parainfluenza virus.

Aspiration pneumonia: There is no evidence to support the use of antibiotics in chemical pneumonitis without bacterial infection. If infection is present in aspiration pneumonia, the choice of antibiotic will depend on several factors, including the suspected causative organism and whether pneumonia was acquired in the community or developed in a hospital setting. Common options include clindamycin, a combination of a beta-lactam antibiotic and metronidazole, or an aminoglycoside.[27] Corticosteroids are commonly used in aspiration pneumonia, but there is no evidence to support their use either.[27]

Pneumonia
Campylobacter Infections Pneumonia Carcinoid Tumors Spleen Diseases Bacterial vaginosis Toxoplasmosis Meningococcal Disease Vaginal Diseases Stomach cancer Ingrown Nail Giardiasis Cardiogenic shock Scoliosis Chronic Diarrhea Urinary Tract And Bladder Infections Aortic Stenosis Mitral Valve Prolapse Colorectal cancer Liver cancer Yersinia Enterocolitica Kaposi's Sarcoma Leukemia, Adult Acute Shigellosis Sickle-cell disease Adenoviridae Coming Soon	Pneumonia Pneumonia is an inflammatory illness of the lung.[1] Frequently, it is described as lung parenchyma/alveolar inflammation and abnormal alveolar filling with fluid (consolidation and exudation).[2] The alveoli are microscopic air-filled sacs in the lungs responsible for absorbing oxygen. Pneumonia can result from a variety of causes, including infection with bacteria, viruses, fungi, or parasites, and chemical or physical injury to the lungs. Its cause may also be officially described as idiopathic—that is, unknown—when infectious causes have been excluded. Typical symptoms associated with pneumonia include cough, chest pain, fever, and difficulty in breathing. Diagnostic tools include x-rays and examination of the sputum. Pneumonia Treatment depends on the cause of pneumonia; bacterial pneumonia is treated with antibiotics. Pneumonia is a common illness which occurs in all age groups, and is a leading cause of death among the elderly and people who are chronically and terminally ill. Additionally, it is the leading cause of death in children under five years old worldwide.[3] Vaccines to prevent certain types of pneumonia are available. The prognosis depends on the type of pneumonia, the appropriate treatment, any complications, and the person's underlying health. Other types of pneumonia Severe acute respiratory syndrome (SARS): SARS is a highly contagious and deadly type of pneumonia which first occurred in 2002 after initial outbreaks in China. SARS is caused by the SARS coronavirus, a previously unknown pathogen. Bronchiolitis obliterans organizing pneumonia (BOOP): BOOP is caused by inflammation of the small airways of the lungs. It is also known as cryptogenic organizing pneumonitis (COP). Eosinophilic pneumonia: Eosinophilic pneumonia is invasion of the lung by eosinophils, a particular kind of white blood cell. Eosinophilic pneumonia often occurs in response to infection with a parasite or after exposure to certain types of environmental factors. Chemical pneumonia: Chemical pneumonia (usually called chemical pneumonitis) is caused by chemical toxicants such as pesticides, which may enter the body by inhalation or by skin contact. When the toxic substance is an oil, the pneumonia may be called lipoid pneumonia. Aspiration pneumonia: Aspiration pneumonia (or aspiration pneumonitis) is caused by aspirating foreign objects which are usually oral or gastric contents, either while eating, or after reflux or vomiting which results in bronchopneumonia. The resulting lung inflammation is not an infection but can contribute to one, since the material aspirated may contain anaerobic bacteria or other unusual causes of pneumonia. Aspiration is a leading cause of death among hospital and nursing home patients, since they often cannot adequately protect their airways and may have otherwise impaired defenses. Dust pneumonia: Dust pneumonia describes disorders caused by excessive exposure to dust storms, particularly during the Dust Bowl in the United States. With dust pneumonia, dust settles all the way into the alveoli of the lungs, stopping the cilia from moving and preventing the lungs from ever clearing themselves. Necrotizing pneumonia, although overlapping with many other classifications, includes pneumonias that cause substantial necrosis of lung cells, and sometimes even lung abscess. Implicated bacteria are extremely commonly anaerobic bacteria, with or without additional facultatively anaerobic ones like Staphylococcus aureus, Klebsiella pneumoniae and Streptococcus pyogenes.[5] Type 3 pneumococcus is uncommonly implicated.[5] Opportunistic pneumonia includes those that frequently strike immunocompromised victims. Main pathogens are cytomegalovirus, Pneumocystis jiroveci, Mycobacterium avium-intracellulare, invasive aspergillosis, invasive candidiasis, as well as the "usual bacteria" that strike immunocompetent people as well.[5] Pneumonia Signs and symptoms People with infectious pneumonia often have a cough producing greenish or yellow sputum, or phlegm and a high fever that may be accompanied by shaking chills. Shortness of breath is also common, as is pleuritic chest pain, a sharp or stabbing pain, either experienced during deep breaths or coughs or worsened by them. People with pneumonia may cough up blood, experience headaches, or develop sweaty and clammy skin. Other possible symptoms are loss of appetite, fatigue, blueness of the skin, nausea, vomiting, mood swings, and joint pains or muscle aches. Less common forms of pneumonia can cause other symptoms; for instance, pneumonia caused by Legionella may cause abdominal pain and diarrhea, while pneumonia caused by tuberculosis or Pneumocystis may cause only weight loss and night sweats. In elderly people manifestations of pneumonia may not be typical. They may develop a new or worsening confusion or may experience unsteadiness, leading to falls. Infants with pneumonia may have many of the symptoms above, but in many cases they are simply sleepy or have a decreased appetite.[8] Symptoms of pneumonia need immediate medical evaluation. Physical examination by a health care provider may reveal fever or sometimes low body temperature, an increased respiratory rate, low blood pressure, a high heart rate, or a low oxygen saturation, which is the amount of oxygen in the blood as indicated by either pulse oximetry or blood gas analysis. People who are struggling to breathe, who are confused, or who have cyanosis (blue-tinged skin) require immediate attention. Physical examination of the lungs may be normal, but often shows decreased expansion of the chest on the affected side, bronchial breathing on auscultation with a stethoscope (harsher sounds from the larger airways transmitted through the inflamed and consolidated lung), and rales (or crackles) heard over the affected area during inspiration. Percussion may be dulled over the affected lung, but increased rather than decreased vocal resonance (which distinguishes it from a pleural effusion).[8] While these signs are relevant, they are insufficient to diagnose or rule out a pneumonia; moreover, in studies it has been shown that two doctors can arrive at different findings on the same patient.[9][10] Cause Pneumonia can be caused by microorganisms, irritants and unknown causes. When pneumonias are grouped this way, infectious causes are the most common type. The symptoms of infectious pneumonia are caused by the invasion of the lungs by microorganisms and by the immune system's response to the infection. Although more than one hundred strains of microorganism can cause pneumonia, only a few are responsible for most cases. The most common causes of pneumonia are viruses and bacteria. Less common causes of infectious pneumonia are fungi and parasites. Viruses Viruses invade cells in order to reproduce. Typically, a virus reaches the lungs when airborne droplets are inhaled through the mouth and nose. Once in the lungs, the virus invades the cells lining the airways and alveoli. This invasion often leads to cell death, either when the virus directly kills the cells, or through a type of cell controlled self-destruction called apoptosis. When the immune system responds to the viral infection, even more lung damage occurs. White blood cells, mainly lymphocytes, activate certain chemical cytokines which allow fluid to leak into the alveoli. This combination of cell destruction and fluid-filled alveoli interrupts the normal transportation of oxygen into the bloodstream. As well as damaging the lungs, many viruses affect other organs and thus disrupt many body functions. Viruses can also make the body more susceptible to bacterial infections; for which reason bacterial pneumonia often complicates viral pneumonia. Viral pneumonia is commonly caused by viruses such as influenza virus, respiratory syncytial virus (RSV), adenovirus, and metapneumovirus. Herpes simplex virus is a rare cause of pneumonia except in newborns. People with weakened immune systems are also at risk of pneumonia caused by cytomegalovirus (CMV). Bacteria Bacteria typically enter the lung when airborne droplets are inhaled, but can also reach the lung through the bloodstream when there is an infection in another part of the body. Many bacteria live in parts of the upper respiratory tract, such as the nose, mouth and sinuses, and can easily be inhaled into the alveoli. Once inside, bacteria may invade the spaces between cells and between alveoli through connecting pores. This invasion triggers the immune system to send neutrophils, a type of defensive white blood cell, to the lungs. The neutrophils engulf and kill the offending organisms, and also release cytokines, causing a general activation of the immune system. This leads to the fever, chills, and fatigue common in bacterial and fungal pneumonia. The neutrophils, bacteria, and fluid from surrounding blood vessels fill the alveoli and interrupt normal oxygen transportation. Bacteria often travel from an infected lung into the bloodstream, causing serious or even fatal illness such as septic shock, with low blood pressure and damage to multiple parts of the body including the brain, kidneys, and heart. Bacteria can also travel to the area between the lungs and the chest wall (the pleural cavity) causing a complication called an empyema. The most common causes of bacterial pneumonia are Streptococcus pneumoniae and "atypical" bacteria. Atypical bacteria are parasitic bacteria that live intracellular or do not have a cell wall. Moreover they cause generally less severe pneumonia, thus atypical symptoms, and respond to different antibiotics than other bacteria. The types of Gram-positive bacteria that cause pneumonia can be found in the nose or mouth of many healthy people. Streptococcus pneumoniae, often called "pneumococcus", is the most common bacterial cause of pneumonia in all age groups except newborn infants. Pneumococcus kills approximately one million children annually, mostly in developing countries.[11] Another important Gram-positive cause of pneumonia is Staphylococcus aureus, with Streptococcus agalactiae being an important cause of pneumonia in newborn babies. Gram-negative bacteria cause pneumonia less frequently than gram-positive bacteria. Some of the gram-negative bacteria that cause pneumonia include Haemophilus influenzae, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa and Moraxella catarrhalis. These bacteria often live in the stomach or intestines and may enter the lungs if vomit is inhaled. "Atypical" bacteria which cause pneumonia include Chlamydophila pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila. Fungi Fungal pneumonia is uncommon, but it may occur in individuals with immune system problems due to AIDS, immunosuppresive drugs, or other medical problems. The pathophysiology of pneumonia caused by fungi is similar to that of bacterial pneumonia. Fungal pneumonia is most often caused by Histoplasma capsulatum, blastomyces, Cryptococcus neoformans, Pneumocystis jiroveci, and Coccidioides immitis. Histoplasmosis is most common in the Mississippi River basin, and coccidioidomycosis in the southwestern United States. Parasites A variety of parasites can affect the lungs. These parasites typically enter the body through the skin or by being swallowed. Once inside, they travel to the lungs, usually through the blood. There, as in other cases of pneumonia, a combination of cellular destruction and immune response causes disruption of oxygen transportation. One type of white blood cell, the eosinophil, responds vigorously to parasite infection. Eosinophils in the lungs can lead to eosinophilic pneumonia, thus complicating the underlying parasitic pneumonia. The most common parasites causing pneumonia are Toxoplasma gondii, Strongyloides stercoralis, and Ascariasis. Idiopathic Idiopathic interstitial pneumonias (IIP) are a class of diffuse lung diseases. In some types of IIP, e.g. some types of usual interstitial pneumonia, the cause, indeed, is unknown or idiopathic. In some types of IIP the cause of the pneumonia is known, e.g. desquamative interstitial pneumonia is caused by smoking, and the name is a misnomer. Pneumonia Diagnosis If pneumonia is suspected on the basis of a patient's symptoms and findings from physical examination, further investigations are needed to confirm the diagnosis. Information from a chest X-ray and blood tests are helpful, and sputum cultures in some cases. The chest X-ray is typically used for diagnosis in hospitals and some clinics with X-ray facilities. However, in a community setting (general practice), pneumonia is usually diagnosed based on symptoms and physical examination alone.[citation needed] Diagnosing pneumonia can be difficult in some people, especially those who have other illnesses. Occasionally a chest CT scan or other tests may be needed to distinguish pneumonia from other illnesses. Differential diagnosis Several diseases and/or conditions can present with similar clinical features to pneumonia and as such care must be taken in the proper diagnosis of the disease. Chronic obstructive pulmonary disease (COPD) or asthma can present with a polyphonic wheeze, similar to that of pneumonia. Pulmonary edema can be mistaken for pneumonia due to its ability to show a third heart sound and present with an abnormal ECG. Other diseases to be taken into consideration include bronchiectasis, lung cancer and pulmonary emboli.[8] Pneumonia Prevention There are several ways to prevent infectious pneumonia. Appropriately treating underlying illnesses (such as AIDS) can decrease a person's risk of pneumonia. Smoking cessation is important not only because it helps to limit lung damage, but also because cigarette smoke interferes with many of the body's natural defenses against pneumonia. Research shows that there are several ways to prevent pneumonia in newborn infants. Testing pregnant women for Group B Streptococcus and Chlamydia trachomatis, and then giving antibiotic treatment if needed, reduces pneumonia in infants. Suctioning the mouth and throat of infants with meconium-stained amniotic fluid decreases the rate of aspiration pneumonia. Vaccination is important for preventing pneumonia in both children and adults. Vaccinations against Haemophilus influenzae and Streptococcus pneumoniae in the first year of life have greatly reduced the role these bacteria play in causing pneumonia in children. Vaccinating children against Streptococcus pneumoniae has also led to a decreased incidence of these infections in adults because many adults acquire infections from children. Hib vaccine is now widely used around the globe. The childhood pneumococcal vaccine is still as of 2009 predominantly used in high-income countries, though this is changing. In 2009, Rwanda became the first low-income country to introduce pneumococcal conjugate vaccine into their national immunization program.[16] A vaccine against Streptococcus pneumoniae is also available for adults. In the U.S., it is currently recommended for all healthy individuals older than 65 and any adults with emphysema, congestive heart failure, diabetes mellitus, cirrhosis of the liver, alcoholism, cerebrospinal fluid leaks, or those who do not have a spleen. A repeat vaccination may also be required after five or ten years.[17] Influenza vaccines should be given yearly to the same individuals who receive vaccination against Streptococcus pneumoniae. In addition, health care workers, nursing home residents, and pregnant women should receive the vaccine.[18] When an influenza outbreak is occurring, medications such as amantadine, rimantadine, zanamivir, and oseltamivir can help prevent influenza.[19][20] Treatment Most cases of pneumonia can be treated without hospitalization. Typically, oral antibiotics, rest, fluids, and home care are sufficient for complete resolution. However, people with pneumonia who are having trouble breathing, people with other medical problems, and the elderly may need more advanced treatment. If the symptoms get worse, the pneumonia does not improve with home treatment, or complications occur, the person will often have to be hospitalized Bacterial pneumonia: Antibiotics are used to treat bacterial pneumonia. In contrast, antibiotics are not useful for viral pneumonia, although they sometimes are used to treat or prevent bacterial infections that can occur in lungs damaged by a viral pneumonia.[citation needed] The antibiotic choice depends on the nature of the pneumonia, the most common microorganisms causing pneumonia in the local geographic area, and the immune status and underlying health of the individual. Treatment for pneumonia should ideally be based on the causative microorganism and its known antibiotic sensitivity. However, a specific cause for pneumonia is identified in only 50% of people, even after extensive evaluation.[citation needed] Because treatment should generally not be delayed in any person with a serious pneumonia, empiric treatment is usually started well before laboratory reports are available. In the United Kingdom, amoxicillin and clarithromycin or erythromycin are the antibiotics selected for most patients with community-acquired pneumonia; patients allergic to penicillins are given erythromycin instead of amoxicillin.[21] In North America, where the "atypical" forms of community-acquired pneumonia are becoming more common, macrolides (such as azithromycin and clarithromycin), the fluoroquinolones, and doxycycline have displaced amoxicillin as first-line outpatient treatment for community-acquired pneumonia.[22] The duration of treatment has traditionally been seven to ten days, but there is increasing evidence that shorter courses (as short as three days) are sufficient.[23][24][25] Antibiotics for hospital-acquired pneumonia include third- and fourth-generation cephalosporins, carbapenems, fluoroquinolones, aminoglycosides, and vancomycin.[26] These antibiotics are usually given intravenously. Multiple antibiotics may be administered in combination in an attempt to treat all of the possible causative microorganisms. Antibiotic choices vary from hospital to hospital because of regional differences in the most likely microorganisms, and because of differences in the microorganisms' abilities to resist various antibiotic treatments. People who have difficulty breathing due to pneumonia may require extra oxygen. Extremely sick individuals may require intensive care, often including endotracheal intubation and artificial ventilation. Viral pneumonia: Viral pneumonia caused by influenza A may be treated with rimantadine or amantadine, while viral pneumonia caused by influenza A or B may be treated with oseltamivir or zanamivir. These treatments are beneficial only if they are started within 48 hours of the onset of symptoms. Many strains of H5N1 influenza A, also known as avian influenza or "bird flu," have shown resistance to rimantadine and amantadine. There are no known effective treatments for viral pneumonias caused by the SARS coronavirus, adenovirus, hantavirus, or parainfluenza virus. Aspiration pneumonia: There is no evidence to support the use of antibiotics in chemical pneumonitis without bacterial infection. If infection is present in aspiration pneumonia, the choice of antibiotic will depend on several factors, including the suspected causative organism and whether pneumonia was acquired in the community or developed in a hospital setting. Common options include clindamycin, a combination of a beta-lactam antibiotic and metronidazole, or an aminoglycoside.[27] Corticosteroids are commonly used in aspiration pneumonia, but there is no evidence to support their use either.[27]
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